1. Field of the Invention
The invention relates to flexible, polymer-modified building compositions and also the use of vinyl ester ethylene copolymers stabilized by protective colloids for flexibilizing building compositions.
2. Background Art
For certain applications in the building sector, for example in sealing slurries or for building adhesives, highly flexible concrete or mortar mixtures are required. In accordance with standards, for example in sealing slurries, use is made of mortar mixtures which are modified with emulsifier-stabilized acrylate dispersions. WO-A 92/07804 (AU-A 9186679) describes binders for flexibilizing building materials, which binders comprise mixtures of polyester resin and styrene-acrylate copolymer--emulsion. EP-A 558980 (U.S. Pat. No. 5,348,993) discloses emulsifier-stabilized styrene-acrylate and vinyl ester-acrylate dispersions as additives for building materials. In the case of these additives, the flexibility is achieved by means of the, polymer component and the use of emulsifiers for stabilizing the emulsion. An overview of the present state of the art for flexibilizing building compositions is given in Volkwein, A; Petri, R.; Springenschmid, R; "Protecting concrete by flexible waterproofing slurries", Betonwerk-Fertigteil-Tech. (1988), 54(8) 30-36, 54(9) 72-78.
A disadvantage of the previously used emulsifier-stabilized styrene-acrylate dispersions is that they can only be used in 2-component systems (component 1=dry mortar, component 2=dispersion), while sufficient flexibilization is not achieved when using redispersible dispersion powders (in 1-component systems) containing the present-day systems (vinyl acetate-ethylene copolymers). However, the great advantage of dispersion powders as compared with the dispersions is that it is possible to produce dry mortar mixtures which only have to be mixed with water on the building site. This brings many advantages such as increased formulation reliability, safe handling and simple disposal of containers. Up to now, there have been no systems based on emulsifier-stabilized vinyl ester copolymer dispersions available which have been able to compete with styrene-acrylate copolymer dispersions in terms of flexibility.
DE-A 4206429 (U.S. Pat. No. 5,348,993) discloses binders for improving the flexibility of building materials based on vinyl propionate-VeoVa9.RTM.(VeoVa10.RTM.).sup.1 emulsion polymers which are prepared in the presence of an emulsifier combination comprising ethylene oxide-propylene oxide polyethers, ethoxylated alkylphenol and ethoxylated polysaccharide. A disadvantage is that sufficient extensibility is not achieved, for example when used in sealing slurries.
EP-A 527322 discloses additives for cement mixtures which comprise ethylene-vinyl acetate-vinyl pivalate copolymers prepared by the emulsion polymerization method in the presence of emulsifier and protective colloid. The improved alkali resistance compared with vinyl acetate-ethylene copolymers is emphasized. A disadvantage is the extensibility which is insufficient for flexibilizing building materials.
EP-A 518406 discloses the preparation of copolymers of ethylene, vinyl acetate and of vinyl esters of .alpha.-branched, tertiary carboxylic acids having 5 or 9 carbon atoms, with vinyl pivalate (VeoVa5.RTM.) being copolymerized in place of VeoVa9.RTM. to improve the degree of incorporation of ethylene. EP-A 295727 relates to ethylene-vinyl acetate copolymers with vinyl esters of .alpha.-branched tertiary carboxylic acids having 9 carbon atoms (VeoVa9.RTM.) or 10 carbon atoms (VeoVa10.RTM.), with copolymers containing VeoVa9.RTM. being recommended in place of VeoVa10.RTM. for paints having reduced tack. The flexibilization of building compositions is discussed neither in EP-A 518406 nor in EP-A 295727.
It is an object of the invention to provide copolymers based on vinyl ester copolymers which are FNT 1. VeoVa5.RTM.; VeoVa9.RTM.; VeoVa10.RTM.; VeoVa11.RTM. vinyl ester are registered trademarks of Shell Corporations covering .alpha.-branched carboxylic acids. suitable both in the form of aqueous dispersions and preferably in the form of redispersible dispersion powders which can be produced from these dispersions for producing highly flexible building compositions, specifically sealing slurries. These copolymers should meet the requirements that the corresponding copolymer dispersions have a strength and flexibility at least equal to the customary styrene-acrylate dispersions but the corresponding dispersion powders effect a significantly better flexibilization than do conventional vinyl acetate-ethylene dispersion powders.